Add solution for LL: reorder linked list

neetcode/linked_list/reorder_linked_list/README.md

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+Reorder Linked List
+You are given the head of a singly linked-list.
+
+The positions of a linked list of length = 7 for example, can intially be represented as:
+
+[0, 1, 2, 3, 4, 5, 6]
+
+Reorder the nodes of the linked list to be in the following order:
+
+[0, 6, 1, 5, 2, 4, 3]
+
+Notice that in the general case for a list of length = n the nodes are reordered to be in the following order:
+
+[0, n-1, 1, n-2, 2, n-3, ...]
+
+You may not modify the values in the list's nodes, but instead you must reorder the nodes themselves.
+
+Example 1:
+
+Input: head = [2,4,6,8]
+
+Output: [2,8,4,6]
+Example 2:
+
+Input: head = [2,4,6,8,10]
+
+Output: [2,10,4,8,6]
+Constraints:
+
+1 <= Length of the list <= 1000.
+1 <= Node.val <= 1000
+
+# Solution
+
+input = [0, 1, 2, 3, 4, 5, 6]
+index = 0
+
+

neetcode/linked_list/reorder_linked_list/solution.py

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+from typing import List, Optional
+
+
+class ListNode:
+    def __init__(self, val=0, next=None):
+        self.val = val
+        self.next = next
+
+
+class Solution:
+    def reorderList(self, head: Optional[ListNode]) -> None:
+        nodes: List[ListNode] = []
+        sorted_nodes: List[ListNode] = []
+        while head:
+            nodes.append(head)
+            head = head.next
+        right = len(nodes) - 1
+        left = 0
+        counter = 0
+        while left <= right:
+            if counter % 2 == 0:
+                sorted_nodes.append(nodes[left])
+                left += 1
+            else:
+                sorted_nodes.append(nodes[right])
+                right -= 1
+            counter += 1
+        for sni in range(0, len(sorted_nodes) - 1):
+            sorted_nodes[sni].next = sorted_nodes[sni + 1]
+        sorted_nodes[-1].next = None
+        return sorted_nodes[0]
+
+
+if __name__ == "__main__":
+    s = Solution()
+    e3 = ListNode(8, None)
+    e2 = ListNode(6, e3)
+    e1 = ListNode(4, e2)
+    e0 = ListNode(2, e1)
+    fe = s.reorderList(e0)
+    while fe:
+        print(f"{fe.val}")
+        fe = fe.next